[infinispan-dev] Ideas for locking improvements

[Mircea Markus]

On 18 May 2011, at 17:23, Manik Surtani wrote:

> 
> On 18 May 2011, at 13:32, Sanne Grinovero wrote:
> 
>>> 1.  Suggesting deferring local locks till prepare-time: wouldn't this create a potentially large number of transaction failures?  Since write skews and overwriting may become a problem if this is allowed.
>> 
>> I agree, but as far as I understood by talking to Mircea this is what
>> the current implementation does: it acquired the locks locally but the
>> key owners don't know about it until commit time.
>> So from that I inferred that - while it surprised me - that if you're
>> able to handle that then you should be able to handle the local locks
>> using the same logic (defferring consistently).
> 
> 
> True, but the way it is right now, at least in the non-clustered case transactions have a much greater chance of completion.
> 
> No harm in 2 separate locking schemes for clustered and non-clustered though.

I don't see how this would cause more failures even on the non-clustered mode: competing transactions fight for same locks in both approaches, just that "the battle" is delayed to prepare time. Especially if we add the lock-reordering optimisation that would result in no-deadlocks, I think the throughput  should be better in both local and clustered scenarios.